A、They planted many trees on mountains. B、They lowered their carbon emissions. C、They set aside many private lands and waters. D

Our country is home to some of the most beautiful God-given landscapes in the world. We’re blessed with natural treasures---from the Grand Tetons to the Grand Canyon; from lush forests and vast deserts to lakes and rivers teeming with wildlife. And it’s our responsibility to protect these treasures for future generations, just as previous generations protected them for us.
Since taking office, I’ve set aside more than260 million acres of public lands and waters---more than any President in history. Last month, we announced that 11 states had come together with farmers, and industry groups to protect some threatened species, without bringing negative influences on the local economies. Two weeks ago, we joined an alliance of countries cracking down on illegal fishing that threatens jobs and food security around the globe. And I’m going to keep protecting the places that make America special, and the livelihoods of those who depend on them.
We’ll also keep doing what we canto prevent the worst effects of climate change before it’s too late. Over the past six years, we’ve led by example, generating more clean energy and lowering our carbon emissions. Our businesses have stepped up in a big way, including just this past week. Some of our biggest companies made new commitments to act on climate---not just because it’s good for the planet, but because it’s good for their bottom line.
This is how America is leading on the environment. And because America is leading by example,150 countries, representing over 85% of global emissions, have now laid out plans to reduce their levels of the harmful carbon pollution that warms our planet. And it gives us great strength going into Paris this December, where the world needs to come together and build on these individual commitments with an ambitious, long-term agreement to protect this Earth for our kids.
After all, as Pope Francis reminds us so eloquently, this planet is a gift from God---and our common home. We should leave it to our kids in better shape than we found it.
Questions 20 to 22 are based on the recording you have just heard.
20. Why does the alliance crack down on illegal fishing?
21. What did Americans do to prevent the climate from getting worse?
22. What’s the speaker’s purpose by delivering the speech?